Psychological Tests Most psychological tests are standardized in the general population (Dobson, 1985). In general, recommendations for the use of psychological and neuropsychological tests in screening for depressive disorders are similar to those for laboratory tests. They are not recommended for routine use in screening for depression. However, in selected cases, psychological and neuropsychological tests may be very useful in differential diagnosis of depression. Neuropsychological tests, such as the modified HalsteadReitan battery, should be considered when it is necessary to distinguish dementia from depression. Depressed patients have been found to show significantly different test profiles on the Minnesota Multiphasic Personality Inventory (MMPI), the Symptom Checklist 90, and the Millon Clinical Multiaxial Inventory than do nondepressed patients with psychiatric diagnoses (Weitzler, Strauman, and Dubro, 1989). While these psychological tests predicted depression at a rate surpassing chance, such instruments were not substitutes for a thorough clinical evaluation. In other words, these tests may confirm, but they do not independently render, the diagnosis. Perhaps the most commonly faced differential diagnosis in primary care practice is that between depressive and anxiety disorders. Dobson (1985) determined that the self-report symptom ratings for these two disorders have poor divergent (discriminative) validity, which is not surprising, since many depressed patients also have anxiety symptoms or suffer from concurrent, co-morbid anxiety disorders. With regard to distinguishing subtypes of depression, the MMPI and Rorschach are of limited value in differentiating major depressive from bipolar disorder and melancholic from nonmelancholic major depressive disorder. In one study, patients with major depressive disorder showed elevated scores on most MMPI scales, compared to those with bipolar disorder, depressed phase (Donnelly, Murphy, and Goodwin, 1976), although subsequent studies failed to replicate this finding (Lumry, 1978; Silver, Isaacs, and Mansky, 1981). Another study found Rorschach responses to be of no value in distinguishing melancholic from nonmelancholic depressions (Carney, Roth, and Garside, 1965). It is not appropriate to use psychological tests, including the MMPI, as the sole means to determine whether a patient with a concurrent symptomatic nonpsychiatric medical illness “really” has a depression, because symptoms from the medical illness itself affect test results. To illustrate, medical patients typically have a depressive/hypochondriacal pattern on the MMPI, because the MMPI somatic symptoms that emanate from the nonpsychiatric medical illness contribute to the depressive/ hypochondriacal symptom scales. In summary, the available empirical data do not support the routine use of self-report or projective instruments to differentiate depression from anxiety disorders. These tests can distinguish depressive from other nonanxious psychiatric conditions, and they can enhance a careful clinical formulation rendered by a clinician well trained in the diagnosis of depressive disorders. Where the differential diagnosis is in doubt, psychological tests may help to tip the balance in favor of one or the other condition. Like laboratory tests, however, psychological tests should not be used for routine screening purposes or administered for all differential diagnostic situations. Ongoing Clinical Reassessment Guideline: A critical element in the differential diagnosis of depressive disorders is ongoing clinical reassessment. (Strength of Evidence = B.) Most patients with major depressive disorder respond partially to medication within 2 to 3 weeks, and full symptom remission is typically seen in 6 to 8 weeks. Most patients receiving time-limited psychotherapy respond partially by 5 to 6 weeks and fully by 10 to 12 weeks. Patients. who fail to show this pattern can be detected through careful interviewing or by clinical or self-report rating scales. In these patients, a reevaluation is indicated. The clinical reevaluations may include repeating a thorough general medical and psychiatric history, physical examination, and a more thorough medical laboratory evaluation. For patients on selected medications, blood level measurements may help gauge whether the serum level of antidepressant is in the therapeutic range. A significant subset of patients with major depression also exhibit maladaptive personality traits or disorders. When the underlying mood disorder is successfully treated, the expression of these maladaptive traits may partially or completely resolve (Joffe and Regan, 1988; Thompson, Gallagher, and Czirr, 1988). However, studies suggest that patients with such preexisting personality disorders are less likely to exhibit a full therapeutic response in affective symptoms to either medication or timelimited psychotherapy, or they may take longer to respond fully. In those who respond only partially to treatment and in whom personality disorders are suspected, psychological testing may be useful to determine the presence of personality disorders. If present, the case for combined treatment with medication and psychotherapy may be stronger. These are general principles whose application to individuals requires judgment, logic, and flexibility. First, it is necessary to define a response, which is usually thought to be at least a 50 percent improvement in baseline (pretreatment) symptom severity or a global judgment that the patient is at least much improved. A remission is defined as either the presence of few or no symptoms or a global patient report of marked improvement. In some cases, other ongoing problems, such as chronic severe life stresses, may slow the response or impair the likelihood of attaining a fully asymptomatic state in 10 to 12 weeks. In such patients, longer observation periods may be needed while treatment continues. Finally, improvement in some symptoms (e.g., insomnia) may not be the best way to judge overall treatment effectiveness. For example, the side effects of medication (e.g., sedation) or psychotherapy (e.g., improved sense of hope or optimism) may result in abatement of selected symptoms while failing to remove all symptoms of the depressive disorder. The timing and type of reassessment, and the interpretation of the results of this reassessment are important. Based on panel consensus and an awareness that most psychopharmacology studies have used assessments conducted every 1 to 2 weeks to evaluate response in efficacy trials, it is recommended that medication treatment visits or telephone contacts initially be weekly to ensure adherence, adjust dosage, and detect and manage side effects. After 3 to 4 weeks, visits may be less frequent for most patients. The degree of response/remission can be assessed at each visit, as well as any evidence of side effects. Whether the clinical interview is supplemented with a symptom-rating scale or not, the practitioner should inventory all of the criterion symptoms of depression included in the patient's initial complaint. 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